1. Field of the Invention
This invention relates generally to hydraulic pressure control valves, and more particularly to such valves having an absolute set pressure which function as a direct-acting sequence valve and a vented counterbalance valve.
2. Description of Related Art
In U.S Pat. No. 4,742,846 I disclosed a direct-acting, differential piston relief valve which exhibits desirable operating characteristics of stability even at very low flows, lack of chattering during opening and low hysteresis. These same characteristics are desirable in pressure control valves used for other purposes. The direct-acting sequence valve and vented counterbalance valve of this invention not only share these operating characteristics, but also utilize many of the same components as the patented valve - making it economical to provide a family of valves.
The two pressure control valves of this invention are insensitive to downstream pressure. That is, they can be set to open at a desired upstream pressure, and this pressure will not vary regardless of the downstream pressure.